A new classification and a synergetical pattern in intracranial hypertension

[Intestinal constipation in patients with intracranial tumors]

The effort that occurs during the Valsalva maneuver provokes a raise in intracranial pressure and may decompensate patients with increased intracranial pressure. The aims of this study were to evaluate the incidence of intestinal constipation in the preoperative period of patients with intracranial tumors and establish a relationship between constipation and intracranial pressure decompensation. This study was performed at the neurosurgery unit of Hospital São Paulo, from August to October 2003, evaluating 37 patients. Preoperative time varied from 2 to 34 days (mean 12 days). During this period, 6 (16.2%) patients underwent constipation; all of them received dietary fiber and lactulose, 2 (33.3%) needed enema administration. All patients performed the Valsalva maneuver during defecation and none of them developed intracranial hypertension decompensation.

Evaluation of a technique of inducing hypertensive renal insufficiency in cats

OBJECTIVE

To compare 2 techniques of inducing combined renal insufficiency and systemic hypertension in cats.

ANIMALS

22 cats 6 to 12 months of age.

PROCEDURES

Cats were randomly assigned to 1 of 3 groups. Control (C) group cats had 2 intact kidneys, remnant kidney (RK) group cats underwent unilateral partial renal infarction and contralateral nephrectomy, and remnant-wrap (W) group cats underwent unilateral partial renal infarction and partial abtation and wrapping of the contralateral kidney. Systemic arterial blood pressure (BP) was measured continuously by use of implanted radiotelemetric devices. Renal function was assessed via determination of glomerular filtration rate, measurement of serum creatinine and BUN concentrations, and determination of urine protein-to-creatinine ratio (UP/C). Serum aldosterone concentration and plasma renin activity were measured on day 75.

RESULTS

Systolic BP was significantly higher in groups RK and W than in group C, and systolic BP was significantly higher in group W than in group RK. Serum aldosterone concentration and plasma renin activity were significantly higher in group W, compared with groups C and RK. Glomerular filtration rate was significantly lower in groups RK and W, compared with group C. Histologic indices of renal injury and UP/C were significantly higher in group W, compared with groups C and RK.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypertensive renal insufficiency in group W was characterized by marked sustained systemic hypertension, decreased renal function, proteinuria, activation of the renin-angiotensin-aldosterone axis, and renal structural injury. Results support the hypothesis that marked systemic hypertension, activation of the renin-angiotensin-aldosterone axis, and proteinuria may damage the kidney of cats with preexisting renal insufficiency.

Simultaneous hypersecretion of CSF and of brain interstitial fluid causes idiopathic intracranial hypertension

Idiopathic intracranial hypertension (IdICH) is a high intracranial pressure and no evidence of intracranial lesions or hydrocephalus. The characteristics of IdICH and the anatomical and physiological data show that the mechanisms of elaboration of the interstitial fluid at blood-brain barrier (BBB) and of cerebrospinal fluid (CSF) at choroid plexus are very similarly. In IdICH many pathological conditions can induce the simultaneous hypersecretion of CSF and of the brain interstitial fluid and the high intracranial pressure (ICP) of CSF is equalized simultaneously of the pressure of the brain interstitial fluid. The cerebral blood flow is maintained quasinormal in IdICH, even increased, so that it occurs a fast absorption of CSF and of interstitial fluid and the brain injury is insignificantly despite the high ICP. Therefore idiopathic intracranial hypertension occurs through simultaneous hypersecretion of the cerebrospinal fluid and of the cerbral interstitial fluid followed by a rapid circulation and absorption of these fluids based on a fast cerebral blood flow.

Idiopathic intracranial hypertension and idiopathic normal pressure hydrocephalus: diseases with opposite pathogenesis?

Idiopathic intracranial hypertension (IDICH) and idiopathic normal pressure hydrocephalus (IDNPH) are disorders of the circulation of the cerebrospinal fluid (CSF) with opposite diagnostic features, obscure etiology but the same treatment: CSF drainage. In both diseases a large quantity of CSF exists: equilibrated by the brain edema in IdICH with high ICP and not equilibrated by brain pressure, and the ventricles are enlarged in IdNPH. The same anatomical structure involved in both diseases is the ventricular wall and this represents a true barrier, a glial-ependymal barrier and it acts as a barrier only in connection with the difference between the pressures. The spontaneous course of both diseases suggests that an open glial-ependymal barrier protects the brain parenchyma.